Hooking Up a Second Battery

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Cybernerd

Member - Posts: 5

Joined: November 28, 2003

Location: United States

Posted: December 12, 2003 at 4:35 PM / IP Logged

Hi -

I read a post that said if you were going to hook up a second battery, to hook them up in parallel. I went to the junkyard today.. and was very lucky, and found a 800cca/1000ca Duralast gold battery for $10. My current battery is a 400cca stock battery. I was wondering if it is safe to wire it with a 4 gage fused wire in parallel (with the Duralast gold in the trunk). If so, how does this work? Does the alternator charge both batteries at the same time? Is it important to get a battery isolator to do this or am I able to just wire them in parallel like that? Also, I would be hooking up my amp and all my aftermarket equipment up to the Duralast battery (in the trunk.) Would this setup prevent my lights from dimming when I have my system running? If anyone has a better setup, or recommends something other than this, please let me know. I just ran into the battery at a great price and didn't want to let the opportunity go by. Just trying to make the best I can with what I am able to get. By the way, my alternator is a stock alternator that is probably about a 70 amp. Thanks.

Teken

Gold - Posts: 1,492

Joined: August 04, 2002

Location: Aruba

Posted: December 12, 2003 at 5:26 PM / IP Logged

1. It would be wise to invest in a battery isolator to prevent both batteries from being drained. As it is now, without an isolator, if you listen to your music with the vehicle off, both batteries will be drained at once.

2. Your current alternator depending upon the age and the condition will be required to work double time. To fully charge both units, as the other battery will simply be another load.

3. It is always recommended that both batteries be of the same in terms age, capacity, CCA. Amp Hour, and reserve.

4. If the battery is not a sealed AGM or similair type. You must ensure that the battery is encased into a battery box, secured, and vented to the outside of the cabin for fresh air.

Failure to include a venting outlet to and from the battery could result in an explosion within the rear trunk cabin.

5. Varify the state of charge of each battery to ensure that they remain above 12.70 to 12.80 VDC .

Regards

EVIL Teken . . .

Geeque

Silver - Posts: 310

Joined: October 07, 2003

Location: United States

Posted: December 13, 2003 at 2:22 PM / IP Logged

Your better off getting a gel cell battery.

Gary Kline

MECP Master Technician

billy1234

Member - Posts: 12

Joined: November 26, 2003

Location: Canada

Posted: December 13, 2003 at 3:17 PM / IP Logged

If you are going to run 2 different types of bats, I would definately recommend an isolator. The main problem is the resistence between the bats. With two different bats there may be a lot of resistence between the two. I have two of the same (Interstate Red Tops) and am not running into any problems. I am not running an isolator yet. About once a month I charge both bats up seperatly with a battery charger. This got rid of all the dimming in my car. I you dont want to run an isolator I would recommend putting the bigger of the 2 bats in the stock location. I hope this helps!!

Clay

Julian59

Member - Posts: 24

Joined: January 31, 2004

Location: United States

Posted: February 02, 2004 at 2:41 AM / IP Logged

Cybernerd

Be smart when installing a 2nd battery always, always use an isolator. The battery isolator you use should always be at least 20% to 30% higher rated then your alternator. ie if you have a 100 amp rated alternator your isolator should be no less then 120 amps. Also your alternator should not drop below 13.5 volts in charging with a load. If it does it needs replacing. Make sure that the cables you use on battery "ONE" are of proper gauge. When installing a battery more then 5 feet from the alternator always use double the gauge wire. Last : make sure you change over all the wiring to the 2nd battery even your radio full time and key power leads, don't use the key to power your radio. What's the point of turning on your key and using the radio for long periods of time and running down the FIRST battery and leaving you stranded. That's why it's call a Battery Isolator. I hope this helps

Julian59

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Hooking Up a Second Battery

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